Open telegraph line indicator



Jan. 13, 1953 F. H. HANLJ-:Y` 2,625,508/` OPEN TELEGRAPH LINE INDICATORFiled July 27, 1948 REPEArE/P l REPEATER {RE/EMM i 'REPEATER Lima/Q4@Effie. 5 1

' /Nl/ENTOR F. H. HANLEV BVM AT TORNEV Patented Jan. 13, 1953` OPENTELEGRAPH LINE INDICATOR Frank Harold Hanley, Butler, NQJ., assignor toAmerican Telephone and Telegraph Company, a corporation of New YorkApplication July 27, 1948, Serial N o. 40,952

3 Claims.

This invention relates to telegraph systems and more particularly to acircuit in a telegraph sys- 'tem for indicating an open telegraph linecondition of longer than a permissible duration.

An object of the invention is the improvement `of open telegraph lineindicator circuits.

There are presently known in the art a number of open telegraph lineindicator arrangements. However, so far as is known there is no existingarrangement for use on complex telegraph transmitting circuits havingmany stations vwhich is effective to both automatically indicate thesection of telegraph line on which the open condition prevails and whichalso automatically informs all stations that the condition is known topreclude the necessity for the calling in by customers to notify of theopen line condition when such trouble exists.

The open line is the most common type of trouble on telegraph circuits.In the modern teletypewriter systems particularly on circuits havingmany stations such trouble causes great difficulty for the `maintenanceforces. The open line usually aifects all drops on a circuit andtherefore in the majority of cases all customers on the circuit willcall the particular maintenance Vforce serving their respective lines toreport the trouble. The diiiiculty caused by this is in proportion tothe complexity of the circuit and the number of customers stationsconnected to the circuit.

In the case of a trouble expectancy of one open circuit per year perrepeater section and livetenths open circuit per year per drop, a simplecircuit of one repeater section and two drors would have two troublesper year and four customers calls reporting the two troubles per year.Assuming the same trouble expectancy on a complicated circuit of fiftysections and one hundred drops there would be one hundred opens per yearand assuming that each open were reported 'by each customer, there wouldbe ten thousand customers calls reporting the hundred trouble conditionson the circuit. On a complicated circuit having fty sections, since atrouble may occur in any one of the fty sections or in any .one of thehundred drops, considerable interoiiice communication and much time arerequired to locate the trouble. In addition, many of the customers callsto report the trouble are made over toll message circuits, and theanswering of the calls tends to delay the work required to sectionalizethe trouble.

The invention herein is designed to reduce -customers calls reportingthe open condition and to reduce the work involved in locating theparticular section on which the open occurs. The open indicator circuitof the present invention isarranged to operate in response to an openline condition exceeding a given maxmum permissible duration from agiven direction and to operate an alarmV in the test room at each end ofa repeater section in which'the open occurs.` The present circuit isalso arranged so that, when it is operated in response to an open, acertain teletypewriter character for example, the letters character issent to every test room and station on the circuit except those twoimmediately adjoining the open section which are notiiied of thiscondition by the operated alarm. The teletypewriter character istransmitted at a iixed uniform rate which may for instance be onecharacter per second. This repeated character serves as an indication tothe customers and to the attendants at-the various test rooms that themaintenance force at the test rooms adjacent .the open has been apprisedof the open condition and that it is not therefore necessary to reportor to sectionalizethe trouble.

The number'of the present circuits required on a particular telegraphinterconnection will depend-upon whether the present circuit is to beused simply in reducing customers calls in reporting the open conditionor is to be used for sectionalizing opens or for other purposes. If itis required only for reducing customers calls in reporting the opencondition it may be installed only at oces serving large numbers ofoutlying drops. If it is to serve for sectionalizing opens, two or moreof the present circuits Will be required at each oiice in the main pathof transmission of the circuit.

The invention may be understood from the `following detailed descriptionwhen read with reference to the associated drawing which taken togetherdisclose a' preferred embodiment of the invention. It is to beunderstood, however, that the invention is not limited to thelparticular `through a embodimen disclosed herein but may be incorporatedin other embodiments which will be readily suggested, to those skilledin the art, by the present disclosure.

Referring now to the drawing: Fig. 1 shows a four-wire direct-currenttelegraph line to the west interconnected to a four- .wiredirect-,current telegraph line to the east an east repeaterV westrepeater and located at the repeater station. Connected to the westrepeater at the'repeater station is an open line indicator circuit. Itis to beunderstood that I6, contact I1 otrelay Y orl spacing contact.

Aleft hand or marking contact andisan open line indicator identical withthat shown connected to the west repeater will ordinarily be connectedto the east repeater in the same mannr as shown for the west repeater.

Fig. 2 indicates schematically a direct-current telegraph system havingsix repeater stations, stations AB, C, D, E and F interconnected intandemv between stations by a four-wire circuit. Each of the stationshas two repeaters indicated by rectangles, shown as RW for a westrepeater and as RE for an east repeater, connected to each of whichrepeaters is an individual open line indicator shown by a rectangle, anddesignated W for the west and E for Athe east open indicator.

In the drawing, the device is shown in the non-operated condition.Conductors land 2Y are the receiving pair of a four-wire telegraphcircuit and may be assumed to extend to a distant repeater to the westand conductors 3 and 4 are Athe receiving pairV of a four-wire telegraphcircuit and may be assumed to extend to adistant repeater tothe east.Conductors 6l and 62 are the sending` pair of the four-wire circuit tothe west and conductors'll and l2 are the sending pair of the four-wirecircuitto the east. When marking current flows in conductors I and 2 thearmature of relay 5 is actuated to engage marking contactv 6. WhenVspacingy current flows in conductors I and 2 the armature of relay 5 isactuated to engage its spacing'contact` 1. When the armature of relay 5'is in engagement with `marking contact 6 a circuit may be traced fromnegative telegraph battery through Vcontact 6 to junction 8-Fromjunction 8, the transmissionbranch of'the circuit extends throughconductor Sto thev apex Il) ot relay'lfl, where it again divides.Themain transmission branch continues through the top winding of relayIl, through resistance l2, contact I3ofdrop jack i4, contact l5 of loopjack 39 andcontact I3 of loop jack I6' to terminal 20; From terminal 20the connection extends in a continuous circuit through other repeaters,indicatedby dotted connection 2i, toterminal 22,Y fromwhich pointV thecircuit continuesV through contact- 23 of' drop where it dividesfintoparallel paths.

jack 24, resistance 25, top winding of Vrelay 26 and the armature and'marking contact 21` o1 relayl 28l to-positive battery. From' apex Illabranch ofthe circuit-extends through-/thebottom windingof relay H andresistance 29 to ground.

In thekcaseof'frelay VI 1,- the-current throughitstopewinding-tendsto-actuate its armature to its right handore'marking contact. Thiseiect is 'opposed by current flowing-throughthe' bottom or biasing winding of relay l l, which effect'tends toactuate the 'armature of relay to its left hand The effect of thecurrent through the topwinding of relay Il, however, is dominant forthis condition'and lthe armature of relay His maintained in engagement'with its right hand or marking-contact. In the case 'ofjrelay 26, theeiectof the current through its top'winding tends toactuate,its-armature'tol its dominant over the effect of currentowing-from positive battery through contact 21, bottom winding of relay26. and resistance 30 to ground, tending to actuate the armature ofrelay 26 towards its right hand or spacing contact, and the armature ofvrelay 26 is maintained in engagement with' its lefthand or markingcontact for-thiscondition. When .the armature ofrelay 5 is actuated toits spacing: contact 1, positive batterylis` connected to each end ofthe circuit through the repeater. No current flows through the topwindings of relays H and 26. The current through the bottom winding ofrelay H is reversed for this condition however, and the armature ofrelay Il is therefore maintained in engagement with its right hand ormarking Contact. Thus relay Il is not aiected by signals transmittedfrom relay 5. In the case of relay 26, as the current through its topwinding falls, its armature is actuated to its right hand or spacingcontact under the inuence of the current through its bottom winding.Thus relay 2B will respond to signals transmitted from relay 5. Whentransmission is from the east repeater toward the west repeater, relay28 will be actuated between its marking and spacing contacts. Relay 26will be maintained in its marking condition while the communicationcontinues in the same manner as was relay Il for the opposite directionof transmission. Relay I l will respond to the signalstransmitted by'relay 28 in the same manner as did relay 26 for the signals transmittedfrom relay 5.

From junction point 8 a branch circuit may be traced which lextendsthrough resistance 32, winding of relay 33'and contact 34 of hit meterjack 35 to positive battery. Relay 33 is a slow to release relay. Whenthe armature ofrelay 5 is maintained in engagement with its marking 33will release.

While relay 33 is in the operated condition, a circuit may be tracedfrom negative battery vthrough'contact 36 and resistance 31 to junction4l, where it branches. One branch extends through contact 38 of relay 39and resistance 4l) topositive battery. From junction point 4l a branchextends' through resistance 42 to the grid of Vspacezdischarge device46, which may, for instance, be a triode having an indirectly heatedConnectedto junction 4l, also, is a negative battery. A circuit maybetracedfrom positive .plate battery through' resistance -45 and thewinding of relayv39l to the plate'of tube 46. Whenthe hit indicatorcircuit is in the-normal unoperated condition, the filament circuitoftube 46 extends` from: negative battery through resistance 41 and thefilament of tube 46 to ground. Insufficient current ows in the filamentcircuit for this .condition to properly heat the indirectly heatedcathode in the tube. When an open'occurs, tube 46 and itsA associatedconnections perform-two functionsintheiprcsent circuit. The filamentcircuit'is used to control the predetermined intervalof'duration ofVan-open lineconditionlforwhich-the circuit is to operate andthegrid'circuit is .usedto'control the lengths yoftlie marking and spacingpulses'comprising the teletypewriter` character which' istransmitted toindicate the open condition to the connected stations and the rate at.which the transmitted character is repeated.'v Thecurrentthrough thekiilament is: controlled by Vthe 1 magnitude. of 'resistance 41 so thatthe time required for the cathode of tube 46 to reach the properoperating temperature may be made to correspond to the duration of anopen circuit condition for which it is desired to have the openindicator circuit operate.

When an open circuit condition of a fixed predetermined length isreceived from the west repeater, relay 33 will release opening contact35, disconnecting negative battery from the top plate of condenser 43.When relay 33 releases, contact 48 will be closed and resistance 49 willbe connected in parallel with resistance 41 in the ilament batterysupply circuit. After a second predetermined interval has elapsed thecathode of tube 45 will reach its normal operating temperature. Duringthis interval condenser 43 will 'be charged by positive battery throughresistance 49 and contact 38. When the grid is made sufiicientlypositive with respect to the cathode, tube 46 will operate, energizingthe winding of relay 39 and actuating the contacts of relay 39 to theiralternate positions.

The opening of contact 38 disconnects positive battery from the topplate of condenser 43. The closing of contact 50 connects negativebattery through resistance 5| and contact 50 to the top plate ofcondenser 43, charging condenser 43 negatively. This, in turn, reducesthe current in the plate circuit to a value below the release value ofrelay 39, so that after a third predetermined interval relay 39releases. Upon the release of relay 39, positive battery will again bereconnected to the top plate of the condenser and the cycle will berepeated. This will continue as long as the open circuit condition ofconductors I and 2 persists and While relay 33 remains released. Thelengths of the intervals during which relay 39 is operated and releasedare controlled by the magnitudes of the potentials of the batteries, theresis-tances 49 and 5I and of the capacitance of condenser 43.

These operated and released intervals are xed so that the letterscharacter in the ve element two-condition telegraph permutation code istransmitted over the telegraph circuit. The letters character isconsidered most suitable for transmission as it has the least eect onteletypewriter copy and causes no damage to the platen of theteletypewriter sets. Tests indicate that this character repeated onceper second is satisfactory. In order to achieve this, relay 39 is heldoperated for about one second and then maintained in the releasedcondition for about twenty-two milliseconds. When relay 39 is operated,the telegraph circuit interconnecting the west repeater and the eastrepeater is opened at contact Il and positive telegraph battery isconnected through resistance 45 and contact 53 to the west repeater. Atthe same time negative telegraph battery is connected through resistance54 and contact 55 to the east repeater. This maintains the west repeaterand the east repeater in the closed condition. When relay 39 is releasedthe transmission conductor is reconnected through the closure of contactIl. However, on such closure of contact Il, when an open conditionprevails on conductors I and 2, relay 5 is in its spacing condition anda spacing signal is transmitted toward the east and through allrepeaters connected to the intact portion of the circuit. This resultsin the transmission of marking signals one second long and spacingsignals twenty-two milliseconds long alternately to all loops andrepeaters on the east side of the circuit, sc that all teletypewriterson drops connected thereto will register repeated letters Each timerelay 39 is operated, lamp 56 will be lighted over an obvious circuitnotifying the attendant that the line to the adjacent station is open.

When the open condition assumed to 'be existing on conductors l and 2 iscorrected, relay 5 will be operated to reengage with its marking contact6. In response to this, relay 33 will be reoperated andthe circuit willbe restored to the normal condition.

If normal communication signaling is resumed as soon as the opencondition is corrected and before the lament of tube 46 has had time tocool off it will cause no diiculty since relay 33 is held operatedduring normal communication and relay 39 will not be again operated.Y

It is to be understood that the open line indicator shown is individualto the west repeater. At each station there are two repeaters connectedin tandem in the telegraph channel, a west repeater and an east repeateras indicated in Figs. 1 and 2. A separate open line indicator individualto the east repeater and connected thereto in the same manner as theopen line indicator shown in detail as connected to the west repeaterwill ordinarily be provided.

When the present arrangement is used for sectionalizing opens, each hitlocater lead, well understood in the art, which usually extends from apoint corresponding to junction point 8 through a hit meter jack, suchas jack 35, to battery, at all test rooms in the main transmission path,will be equipped with one of the present circuits. Under such conditionsassuming test rooms A, B, C, D, E and F connected in tandem, inalphabetical sequence; in the main transmission path, as indicated inFig. 2, when an open occurs on the main path, the particular openindicator circuit at each of the test rooms connected directly to theterminals of the section in which the open occurs, and these two openindicator circuits only, will 'be operated. For example, if an openoccurs between test rooms C and D, the east open indicator at station Cand the west open indicator at station D will both be operated and theiroperation will cause long marks and short spaces, corresponding to theletters signal combination in the multielement permutation telegraphsignal code, to be sent to all of the other test rooms on the circuit.The code combination transmitted from test room C will be received attest rooms B and A while that transmitted from test room D will bereceived at test rooms E and F. This continued transmission prevents therelease of the relay corresponding to relay 33 at all other ofiices andthus prevents the open indicator circuit from operating at all pointsother than at the terminals of the section in which the open occurs. Thelighting or lamp such as lamp 56 in the open indicator circuit at eachof test rooms C and D will serve as an indication that the open existsin the circuit between these two test rooms.

In order to prevent the momentary operation of the open indicatorcircuits at test rooms other than those adjacent to the trouble, thetiming of the devices on each direction of transmission may be made ofprogressively longer duration for each succeeding oiiice along thetransmission path.

When an open occurs on a section of a side leg to an outlying point,that oice only which is Yline to said receiving relay, atelegraphopen-line indicator. .circuit connected intermediate adirst and` a .secondof said. repeaters. and directly .to a first receivingl relay in a rstof. saidarepeaters, signalmeans insaid circuit operative in response to`anopen condition of said lineranda-respon -sive protracted spacingcondition of .saidrst relay, to indicate that` said line is .open,'saidmeans comprising a second relay. slowly responsive tosaidspacingcondition of said rst relay, a space discharge device responsiveYto said second relay, a third relay for transmitting a per- 4mutationcode signal combination responsive to said space discharge device, aninput circuit'for -saiddevice` and a condenser-resistance timingvcircuit connected to said input circuit, lsaid timing circuitresponsive to said third vrelay'.

` 2. A direct-current telegraph systernhaving a telegraph line directlyinterconnecting aplurality of ydirect-current telegraph repeatersintandem along said line, eachof'said repeaters com-V prising apolar'te'legraph sending relay for impressing direct-current nsigna-1conditions directly on said line, each of said repeaters comprising alsoa polar telegraph receiving relay forreceiving directfcurrent signalconditions directly from said line, an individual openlineindicatorcircuit connected to saidsendigand receiving relaywin each of saidrepeaters, ,means in said indicator circuit, including a spaceydischarge device responsive to 'a protracted spacing con-r y ditionofthe receiving'relay in itsconnectedre- :.peater for. operating a,permutation code isignal trai'ismitter.iisaid indicatr'circuit, totransmit `a"prniutatio codeffsignal combination 'characterizin`g"saidcondition' vover th'e'rintact' portion v"ofi Vsaidline,said transmittercomprising a condenser-resistance vtinfiing circuit connectalolel tom'the inputof said .spacedischargedeviceand' a relay inthe outputcircuitof said device `.responsive tosaid .device to control -the connection ofsaid l timing circuit .to Ysaid input, circuit.

' 3. `A `directcurrentllegraph system having` a vdirectcurrentItelegraph line, 'a directfcurr'ent A telegraphrepea'ter saidline, 'atelegraph signal receiving .element in 'said repeater directlyconnectedto and .responsive 'bedirect-current telegraphlsignals 4inlsaidline, al permutation., code .telegrapliffsignal transmitter ,open lineindicator circuit connect.ed tolsaid line, said circuitc'om-V'prisingfa.space .discharge ,device having an input and ;anoutput`circuit, jaffrsti control f oisaid Hinput'. CirCuitresponsive Lto/saidelement, said control '.actuable to a.` particular condition responsiveto a protractedjspacing conditionof Ysaidline, a second .controller saidinput circuit connected,to and responsive tor said output circuit,@condensereresistance vtiming circuit, con- ,nectable to. said. inputcircuit ,responsive to `said second control, landl means 'responsive'to. said seco'ndcontrol forimpressing aperniutation code *signalcombination ,on ,Lsaid-. line' to indicate an 'Open-Conditmn 0fsaidline.

H AROLD HANLEY.

` REFERENCES CITED Thefollowing .references areof record inthe file.ofthis. patent:

unrrnn sijn'rEs PA'rirrrrs Name n Number Date '1,735,041 ,Gardner Nov.12, 1929 1,749,048 Thorp' Mar. 4,1930 1,757,225 Singel May 6, 1930 Y2,009,447 Hart July 30, 1935 -2,409,229 smith Oct.' 15, 1940 @2415;093YlLGi-:irwi'n Feb. 4, 1,947

